Yanjin, a city built along the Yangtze river in southern China, is the narrowest in the world: just 30 metres wide in some places. But despite growth being constrained by the area's stunning geography, residents have managed to turn this former mountain trading hub into a bustling metropolis of some 400,000 people. The once-isolated city has been thrust into the spotlight by Chinese social media users, who made drone footage of Yanjin go viral. With just two streets running along each bank of the river, the city is hoping to capitalise on its newfound popularity and attract more and more tourists. Our France 2 colleagues report, with FRANCE 24's Camile Nedelec.